Center-hole grinder



Dec. 22 19 0 I H. F. wENsoN 3,543,545

' CENTER-HOLE GRINDER 7 Filed April 4, 1969 v B SheetS-Sheet l INVENTOR.

I l? j I HENRY F sws/vso/v v BY M H. F. SWENSON CENTER-HOLE GRINDER Dec. 22 1970 8 Sheets-Sheet 2 Filed April 4, 1969 INVENTOR.

HENRY F. SwE/vso/v GENT H. F. SWENSON CENTER-HOLE GRINDER Dec. 22, 1970 8 Sheets-Sheet 5 Filed April 4, 1969 W R WE/N N 5 15 F y R M m? H Y B Dec. 22, 1970 H. F. SWENSON 3,543,545

I CENTER-HOLE GRINDER Filed April 4, 1969 8 Sheets-Sheet 4 INVENTOR. HENRY F SWENSON AaE/vr.

Dec. 22, 1970 v H. F. SWENSON 3,543,545

' CENTER-HOLE GRINDER Filed April 4, 1969' a Sheets-Sheet s INVENTOR. HENRY F $wE/vs0/v AGENZ Dec. 22, 1970 H. F. SWENSON 3,543,545

GENTER-HOLE GRINDER Filed April 4-," 1969 s Sheets-Sheet e INVENTOR. HENRYF. SWENSO/V GENT.

Dec. 22, 1-970 H. F. SWENSON CENTER-HOLE GRINDER 8 Sheets-Sheet '7 Filed April 4,' 1969 INVENIOR.

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HENRY F. SWENSON AGENT United States Patent O 3,548,545 CENTER-HOLE GRINDER Henry F. Swenson, 22 Holmehill Lane, Roseland, NJ. 07068 Filed Apr. 4, 1969, Ser. No. 813,592 Int. Cl. 1524b 5/00, 29/00, 37/00 U.S. c1. s1 s0 35 Claims ABSTRACT OF THE DISCLOSURE A center-hole grinder is adapted to accurately grind the center-hole portions of the ends of workpieces so that the finished ground center-holes are concentric to vital or determined reference points whether they are inside or outside configurations of the workpiece. The grinder apparatus causes the workpiece to be rotated and supported in a generally vertically disposed steady rest with the workpiece inclined at a slight angle, such as four degrees from the vertical, so as to rest against two support points of a V-type steady-rest. The thirty-degree slope of the finished center-hole of the workpiece is preferably ground to produce a center-hole whose sidewall has a slightly convex radius.

BACKGROUND OF THE INVENTION Field of the invention The field of art to which this invention pertains is generally found in the class entitled Abrading and particularly in the subclass entitled machines and more particularly in the subclass entitled rotary tool and the further subclass pertaining to apparatus in which there is a rotary work holder.

DESCRIPTION OF THE PRIOR ART The grinding of the center-holes provided in the ends of shafts in chamfered internal shoulders in lengths of tubing and the like has been a more or less standard and desired procedure for those workpieces which have been heat treated prior to a final grinding and finishing of the workpiece to its final dimensions. The grinding of the center-holes concentric to the various vital reference points of the workpiece, whether these points are inside or outside the configuration of the piece, is a necessary step in the production of an accurate final workpiece. Conventional center-hole grinding apparatus may be a planetary center-hole grinding device or may use a gripping means such as a chuck to rotate the workpiece while a rotating grinding stone is advanced into the center-hole.

In the use of a planetary grinding apparatus, the workpiece must be indicated to avoid misalignment and a like procedure is usually used when the piece is chucked for grinding. One attempt to avoid the necessity of indicating the workpiece is shown in the center-hole lapping apparatus shown in the US. Pat. 3,187,470 to Arneson of June 8, 1965. In this apparatus the center-hole of the workpiece is ground to provide a spherical recess, which generated hole allows a certain amount of misalignment of the workpiece and requires ball-type centers for the support of the workpiece during the finish grinding operations. Ball-type centers used in grinding apparatus are centers which are highly special and are undesirable in most machining operations.

As above-noted, the use of planetary grinders for cen- 3,548,545 Patented Dec. 22, 1970 ice ter-hole grinding incurs many inherent problems, including the necessity of indicating vital parts of the workpieces to avoid, as much as possible, any misalignment of the workpiece. The planetary rotation of the grinding head is about a fixed axis and as the workpiece, whose center-hole is being ground, is held in a stationary device, the probability of holding the workpiece so that its axis is precisely concentric with the center-hole being ground is extremely diflicult. If the concentricity of the part to the center-hole is to be held to extremely close tolerances, such as a few ten thousandths of an inch, the possibliity or probability of easy production of such tolerances is quite diflicult. In particular, as the usual use of center-holes is in workpieces such as shafts and the like, the conventional workpiece to be ground and requiring center-holes usually has two center-holes (one on each end) and the workpiece has been heat treated. In the heat treating there is a great likelihood of the workpiece being skewed so as to alter the alignment of the workpiece with the previously formed center-holes. Conventional lapping or plunge grinding of these holes does not correct this misalignment as the lapping or plunge grinding of the center-hole tends to follow the existing error formed during preliminary machining or during heat treatment.

Misalignment of the lapped center-holes is often discovered or confirmed by rotating the workpiece between centers. The misaligned center-holes will have a sufiicient oifset in height and parallelism so that the misaligned center-holes, as the workpiece is rotated on fixed centers, will alternately bind and become loose. This misalignment occurs at one point of the rotation and provides a small camming effect causing the part to spring the centers of the apparatus or to bow the workpiece. If this misalignment condition is not corrected, the grinding of any ground diameters on the workpiece will produce thrustcarrying shoulders on the workpiece which are out of square with the axis of the workpiece, which then results in a defective workpiece or results in an unwanted concentrated load on a thrust-carrying bearing and very often causing failure of these bearings.

The roundness or trueness of the center-hole has a direct bearing on the accuracy of the cylindrically ground portion of the workpiece as an oval center-hole permits the workpiece to shift during the grinding of the journal or other cylindrical surfaces of the workpiece. The wheel pressure of the grinding machine tends to force a movement of the part against the centers of the machine, and so the workpiece having an oval center-hole will move twice in one revolution with the resulting ground surface or surfaces elliptical in final configuration. If both ends of the workpiece have their center-holes ground oval to provide like conditions, the workpiece, as it is ground, shifts both regularly and angularly resulting in a workpiece with poor roundness and with the shoulders of the ground portions not square to the diameters and, in addition, the ground surfaces have a poor surface finish because of irregular pressures on the surfaces being ground.

SUMMARY OF THE INVENTION In the center-hole grinder here and after more fully described, the workpiece is held in an upright condition with its axis sloped about four degrees off a precise vertical line. The workpiece rests on its bottom center and is supported near its upper end where it rests in an upper adjustable V-assembly steady-rest. This steady-rest in a preferred embodiment has magnets adjacent its receiving or supporting points. These support points of the adjustable steady-rest are disposed to accept and journal the workpiece being ground with the axis of the points being positioned at a sixty-seven and one-half degree angle to a theoretical center line or with a forty-five degree included angle. This arrangement permits a preferred seating of the journal of the workpiece on its outer diameter so that any run-out of the part is held to a minimum condition. This V-assembly steady-rest in its preferred and alternate embodiments is mounted on a pair of parallel shafts, each carried in a pair of aligned and spaced ball bushings. The body of the V-assembly is maintained in a determined position by an adjustable spring-loaded plunger which allows the V-assembly steady-rest holding the workpiece to oscillate horizontally in response to the thrust of the grinding wheel as the grinding point or wheel enters the center-hole to grind said hole. The grinding point is reciprocated vertically and in its cycle path is brought into contact with the inner or backside of the center-hole, and with this pressure the workpiece is moved inwardly against the spring bias on the downstroke of the grinding wheel and by the spring bias is moved outwardly on the up-stroke of the grinding point. This horizontal oscillation of the workpiece produces a resulting grinding action up and down the side of the center-hole so that a slight radius is generated on the thirty-degree side of the center-hole. This radius which is generated on the thirty-degree side of the center-hole is quite accurate and is convex and is accurately positioned as far as the supporting journal surface is concerned. A center-hole having a convex curved formation provides a single line contact with an accurately ground straight-sided supporting center. Such a center-hole insures an accurate support of the workpiece as its journal and other cylindrical portions or surfaces are ground.

It is an object of this invention to provide a center-hole grinder wherein the workpiece is vertically supported with a slight slope rearwardly. The workpiece at its upper end is supported in a V-type steady-rest which is springbiased and carried in means providing for oscillating of the steady-rest. The grinding point is reciprocable vertically and, as it grinds the backside of the center-hole, a grinding action is produced which generates an accurate convex-shaped center-hole.

It is a further object of this invention to provide a center-hole grinder in which the trombone action of the V-type steady-rest may be locked so that an accurate straight-sided center-hole may be generated.

INTENT OF THE DISCLOSURE Although the following disclosure offered for public dissemination is detailed to insure adequacy and aid in understanding of the invention, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how it may later be disguised by variations in form or additions of further improvements. The claims at the end hereof are intended as the chief aid toward this purpose, as it is these that meet the requirement of pointing out the parts, improvements or combinations in which the inventive concepts are found.

There has been chosen a specific embodiment of the center-hole grinder and trombone-style steady-rest for grinding the center-holes of shafts and the like. This specific embodiment and alternate embodiments of the steady-rest have been chosen for the purposes of illustration and description as shown in the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a perspective view of the center-hole grinder of this invention wherein is shown the general arrangement of the various eomprnonents comprising the apparatus except for the location of and showing of an adjustable V-type steady-rest;

FIG. 2 represents a partial and partly diagrammatic side view of the grinder particularly showing the relationship of the base column and drive table elevating screw drive;

FIG. 3 represents a plan view of the drive table and with the T-bar way support portion thereof shown in section;

FIG. 4 represents a sectional View of the drive table, the view taken on the line 44 of FIG. 3 and looking in the direction of the arrows;

FIG. 5 represents a plan view of a V-type steady-rest and a horizontal support therefor which is vertically movable along a T-bar way portion of the column, the V-type steady-rest adapted to provide a trombone-type action as it supports the upper portion of a rotating workpiece;

FIG. 6 represents a side view of the V-type steady-rest of and with the view taken on the line 66 of FIG. 5;

FIG. 7 represents a plan view of a V-type steady-rest or work holder support of alternate construction;

FIG. 8 represents a side view of the V-type steady-rest of FIG. 7 and with the view taken on the line 88 thereof and looking in the direction of the arrows;

FIG. 9 represents a plan view of yet another alternate construction of a V-type steady-rest or work holder support;

FIG. 10 represents a side view of the V-type steady-rest of FIG. 9 with the view taken on the line 10-10 thereof and looking in the direction of the arrows;

FIG. 11 represents an exploded isometric view and relationship thereof of most of the components forming the head portion or member of the center-hole grinder;

FIG. 12 represents a sectional plan view of the grinder motor support and showing a means for clamping the motor support in a desired or selected position on a pair of vertical guide rods;

FIG. 13 represents a partly fragmentary sectional view taken on the line 13- 13 of FIG. 14 and showing an adjustable support for a dressing diamond for a grinding stone as carried in a grinding motor;

FIG. 14 represents a side view showing a general arrangement of a dressing arm and the diamond dresser carried thereon;

FIG. 15 represents a fragmentary side view showing the diamond dressing head and its means for adjustment as it is brought into a position for a dressing engagement with the grinding stone;

FIG. 16 represents a diagrammatic sectional view of a center-hole ground with a convex side wall;

FIG. 17 represents a side view mostly in section of a swing arm arrangement and adjustment thereof, and

FIG. 18 represents an enlarged sectional view of a thrust bearing and a dirt guard and drag means.

In the following description and in the claims, various details will be identified by specific names for convenience; these names, however, are intended to be generic in their application. Corresponding reference characters refer to like members throughout the several figures of the drawings.

The drawings accompanying and forming part of this specification disclose certain details of construction for the purpose of explanation of the broader aspects of the invention, but these structural details may be modified in various respects without departure from the concept and principles of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and in particular to FIG. 1, wherein is shown a preferred embodiment of a center-hole grinder generally designated as 20, this grinder includes a base cabinet 22 which has mounted thereon a pedestal member 24, which pedestal is bolted or otherwise attached to the top surface of the cabinet 22. The pedestal extends upwardly to support and retain a movable head member 26 on its upper end. Carried on the front portion of this head member is a reciprocally movable motor housing bracket 28 which is adapted to receive and retain a high speed grinder 30.

The cabinet 22, in the exemplified version, is provided with an access opening which is covered by a door or panel 32. Within this cabinet the various electrical controls and other power equipment are contained and the cabinets outer covering acts to provide a shield from exposure, tampering and accidental contact with these various controls.

FIG. 2 provides a partly diagrammatic view of the base 22 and shows a lead screw 40 generally carried by the base 22. The positioned lower support of the lead screw includes a support bracket 42, which bracket is attached ot the base 22. A tapered roller bearing 44 is carried in this bracket and this bearing rotatably retains a collar member 46 which is shouldered so as to support the lower reduced end of the screw 40. A retaining shield 47 also carried by the bracket is disposed to prevent dirt from entering the bearing 44, as does a like retaining shield 48 mounted in the bottom part of the bracket.

Carried on the reduced lower end of the screw 40' is a timing-belt pulley 50 which is driven by means of a motor 52 carried within the base cabinet. This motor has a timing-belt pulley 54 mounted thereon and drives a timing-belt 56 which also engages and drives pulley 50. The upper end of the screw 40 is carried by a bearing bracket 60 which is attached to the top of a T-bar or rail 66 attached to the face of the pedestal 24. It is to be noted that, as disposed, both the pedestal face and the screw 40 are tilted rearwardly at an angle of about four degrees from a vertical condition. The bracket 60 is positioned below the top of the pedestal casting 24 with the top of the casting finished to provide a support for the head member 26 to be more fully described hereinbelow. The face of the casting pedestal 24 and base 22 are finished to provide a precise support surface for the T-bar or rail 66 which has an undercut 68 formed on each side thereof to provide a gripping slide support for a work support table 70.

Referring now to FIGS. 3 and 4, it is to be noted that a work support table 70 is disposed to be slidably carried on the That 66 and has L-shaped clamp members 72 and 74 each carried by cap screws 75 which threadedly engage the cast body 76 of the worktable. Wear strips 78 and 79 are retained in notches in the cast body and are disposed between the inner surfaces of clamp members 72 and 74 and worktable 76 so as to engage the face of the outwardly extending portions of the T-bar 66. Carried at a selected central position of the table 70 is a rotating center and drive unit which includes a shouldered socket member 82 rotatably supported by a thrust bearing 84 and axially maintained in a bearing 86. This member 82 is formed with a socket adapted to removably retain a center 88 which has a reduced end portion which, as shown, has mounted thereon a timing-belt pulley 90. This pulley is rotated by a timing-belt 92 driven by a motor 94 carrying a driving timing-belt pulley 96 mounted on its extending shaft member. A drive pin 98 may be carried in the member 82 to rotate therewith so as to engage a drive dog or the like which is attached to a workpiece, not shown.

Referring now again to FIG. 1, it is to be noted that the power for the motor 94 is preferably supplied by means of a coil-cord type electrical conductor 100, which conductor extends to and into the cabinet 22 in a manner so as to allow the worktable 70 to be moved up and down by means of the rotation of the screw 40. The gear motor 52 is reversible and rotates the screw 40 either in a clockwise or counterclockwise direction. As the screw rotates it engages a threaded nut 104 mounted in the cast body 76 to cause the worktable 70 to be moved up and down.

Referring now in particular to a preferred embodiment of an upper work support or V-type steady-rest 110 as seen in FIGS. 5 and 6, wherein a support body has a cutout 122 which is shaped and disposed to engage and slide upon T-bar 66, the screw 40, by means of clearance hole 124, passes through body 120 without affecting the selected position of the body. This body 120 is also provided with drilled passageways in which a pair of parallel shafts 126 and 128 are reciprocably retained in ball bushings 130 mounted in shouldered recesses in the passageways. Shafts 126 and 128 may be locked into position in the passageways by means of knurl-headed clamp screws 132 and 133. Carried on the ends of these shafts 126 and 128 is a support bar 136, which bar, as shown, has a dovetail formed in its upper side. The upper edges of bar 136 are beveled and carry thereupon righthand and left-hand slide blocks 138 and 139, which slide blocks are contoured to mate with the upper beveled edges and surface of the bar 136. Within the dovetail there are carried slide nuts 141 and 142 which are threaded to receive the inner ends of thumb screws 144 and 145.

Carried in the outer end portion of each of the slide blocks 138 and 139 are support pins which, in the present case, are thumb screws and 151 made of brass and which have their inner ends polished or otherwise contoured to slidably engage and support a workpiece 153. These screws are carried at an angle of about twenty-two and one-half degrees to the outer face of bar 136. Blocks 138 and 139 are contemplated to be made of a material which is antimagnetic. Within each of these blocks there is provided and mounted cylindrical magnets 156 and 157 joined at their ends to improve their magnetic field by means of conductors 159 and 160. Each magnet is insulated from the screw passing therethrough by means of a plastic bushing 162 or 163.

Carried in and by the bar 136 and midway between shafts 126 and 128 is a threaded plunger body member 166 which is rotated for in-and-out adjustment by grasping a knurled portion 168. Within adjusting member 166 is slidably retained a compression spring 170 which engages one end of a plunger pin 172. The other end of the spring engages the inner shoulder end of body member 166 so as to provide a spring-urged outward thrust to the body member 166. A slide stop 176 is carried by a shouldered screw 178 and is slidable into and out of engagement with the inner end of the threaded adjusting member 166.

In the somewhat diagrammatic side view of FIG. 6, it is to be noted that clamp screws 132 and 133, when tightened against shafts 126 and 128, lock these shafts and the steady-rest 110 against reciprocable movement in ball bushings 130. When the clamp screws 132 and 133 are released from engagement with their respective shafts the V-type steady-rest 110 is free to move in the bushing 130. The blocks 138 and 139 are adjusted by sliding along bar 136 and are clamped in place by tightening screws 144 and 145. In the grinding of the center-hole of the shaft 153, a grinding stone point 179 is caused to engage the rear or inner side of the hole nearest the support bar 136.

Referring next to an alternate V-type steady-rest 180, as seen in FIGS. 7 and 8, it is to be noted that the shafts 126 and 128 carry bar 136 in the manner of the FIGS. 5 and 6 above-described. A pair of support blocks 181 and 182 are formed to provide a forty-five degree included support surfaces 183 and 184. These inside surfaces are of material or treatment which provide a surface of a minimal sliding friction. Mounted on and retained in block 181 is a clamp member 185 which, by means of a screw block or clamp 186, may be moved in and out of retaining engagement of a rotatable workpiece 188 which, as shown, is a tube. This tube, which is shown in phantom outline, may have its inner shoulder chamfered at 189 and by means of a grinding stone 190 this chamfer is ground concentric and true to the support surfaces 183 and 184. The sequence of operations to perform this grinding operation is more fully described hereinbelow.

Referring next to an alternate steady-rest assembly 191, as shown in FIGS. 9 and 10, it is noted that the shafts 126 and 128, as above-described, carry bar 136 upon which is mounted a pair of support blocks 192 and 194. Block 192, in the manner of block 181, carries a retaining rod or clamp member 185 in a screw block 186. Workpiece 195, instead of being supported in a V-way, is supported by two antifriction bearings mounted as rollers 196 and 198 carried respectively on the outer ends of the support blocks 192 and 194. As seen particularly in FIG. 9, these rollers are positioned so as to engage the inner surface or diameter of the rotated workpiece 195 which, in this particular instance, as shown in phantom outline, is a tube having an internal chamfer 200, which chamfer, of course, is to be ground by the center-hole grinder of this invention. As a matter of design, it is to be noted that the outer edges 202 and 203 of blocks 192 and 194 are formed at a determined angle and are faced with material providing a satisfactory sliding surface to support a workpiece. Thus constructed, the blocks 192 and 194 may be reversed on bar 136 so that the now facing edges 202 and 203 provide a forty-five degree included V-support surface. Cutouts or relief portions 206 and 207 are provided so that a grinding stone, not shown, but in the manner of FIG. 8 may easily engage the inner edge of chamfer 200.

Referring next to FIG. 11, there is shown an exploded view of several of the components comprising the head member 26. These components include a support block 220 which is attached as by cap screws 221 to a slide plate 222 which has formed therein a slot 224 through which a toothed rack 226 extends. This rack is attached to the block 220 so that the toothed portion extends downward- 1y. The sides of slide plate 222, which are preferably of hardened steel or cast iron, have their outer edges 230 and 232 contoured so as to be slidably retained in a dovetail slide provided in top of the support pedestal 24. As seen in FIG. 1, the head member 26 is seated on the top of the pedestal 24 and is contemplated as being movable by means of a knob 236 which is attached to a shaft, not shown. A pinion, not shown, is connected to and is rotated by the shaft. The shaft and attached pinion are carried in the pedestal 24 so tnat the teeth of the rack 226 are engaged by he pinion and as the rack is moved forwardly and rearwardly, the head member 220 is also moved back and forth in the dove-tail in the pedestal 24. Clamping means is provided on the pedestal on the side opposite knob 236. This clamping means is used to lock the member 220 in position after it, the member, has been moved to the desired position on the pedestal.

Referring to FIGS. 1 and 11, it is to be noted that motor 30 is carried in housing bracket 28. This bracket is adapted to be cycled vertically by the manipulation of a lever 240. This lever is attached to a shaft 242 by means of a pin 243 and rotates shaft 242 as it extends through aligned holes formed in the block 220, hole 244 being the visible near hole. A pinion 245 has set screws 246 and 247 rotatably mounted in its hub. These set screws are disposed to engage recesses 250 and 251 formed in the shaft 242 and to axially position the pinion on the shaft. The left end of the shaft 242 is provided with a slot 253 which is adapted to engage the inner end of a coil spring 254. The other or outer end of the coil spring is bent outwardly so as to engage a retaining slot 256 formed in an edge of recess 258 which is adapted to retain the spring 254. A cover 260 is attached to the side of block 220 by means of screws 262 whose threaded ends enter tapped holes 264 to draw the cover into the recess 258, thus retaining the spring 254 in position. The sides of the pinion 245 are spaced so as to provide a sliding fit between the sidewalls of the recess 265 formed in the end of the block 220. With the pinion 245 attached to the shaft by set screws 246 and 247, the shaft 242 is axially retained and positioned in block 220.

In the front of block 220 is carried a pair of shafts 266 and 267 which is disposed in aligned pairs of holes 268 and 269, 270 and 271. These shafts are of a sufiicient length so as to extend through the Opening or recess 265 and be retained in the upper and lower wall portions surrounding this recess. The block 28 has a through bore 275 formed in its outer portion. This bore is disopsed and sized to engage and retain the shank or retaining collar portion of a grinding motor 30. The back end of block 28 is contoured to provide an inwardly extending portion 277 within which there is disposed a pair of aligned through holes 279 and 280. Mounted in these holes are ball bushings, of which those identified as 281 and 282 are seen. Like ball bushings are provided at the lower end of each of the holes in block 28. These ball bushings are sized to slidably engage and move on the shaft 266 and 267 after they are mounted in block 220. A rack 283 which is seen in FIG. 12 is carried on the rear surface of motor block 28 and is disposed so that its toothed portion is engaged by the pinion 245 when and after the head is assambled. As the lever 240 is manipulated, the shaft 242 and the attached pinion 245 are rotated to cause the motor block 28 to be cycled up-anddown so as to bring the grinding stone carried and rotated by the motor 30 into and out of engagement with the center-hole to be ground. A set screw 284 mounted in the front of motor block 28 is disposed to enter bore 275 and lock the mounted motor 30 therein.

Referring next to FIG. 12 and the motor bracket 28, shown in section, it is to be noted that means are provided to engage shafts 266 and 267 and lock this block 28 in a predetermined axial position on the shafts. This locking means includes a thrust bar 290 sized to be retained in a cross drilled hole 292. The ends 293 and 294 of the bar are beveled and sizes so as to lie contiguous to the sides of the shafts. A notch 296 is formed midway of the ends of the bar and on the side of the bar opposite the notch, the bar is tapered at 298 and 299 to insure that the bar may be slightly bent at the notch and so that the end portions move toward bore 275. Balls 301 5'55 302 are carried in bore 304. A thumb screw 306 is threadably carried in mating bore 308 and has a tapered end 309 disposed to engage the ball 301 and urge it toward bar 290.

Referring next to FIGS. 13, 14 and 15, there is shown an adjustable diamond dressing means for truing a grinding stone carried in the motor 30. In support block 220 there is provided a sloped recess 310 (also seen in FIG. 11) in which a threaded hole 312 is disposed to removably retain a socket head cap screw 314. A short leg member 316, having a shouldered slot 318 longitudinally disposed therein, is slidably mounted in recess 310 and is clamped therein by tightening screw 314. Pivotally carried on the depending or lower end of leg member 316 is swing arm 320. As shown, this pivot connection is provided by means of a shouldered cap screw 322. The other end of arm 320 carries a diamond dresser 325 which, as seen in FIG. 15, has a large face so that in dressing a grinding stone 327 a flat or straight line may be generated. The large face of the dresser is of a selected size so that in the swinging of the dresser the are transcribed thereby in dressing the stone is not greater than the diameter of the effective grinding face. In this manner a straight face on the dressing stone is produced rather than a curved face which is produced by a transcribed arc of a single point diamond dresser. The dresser 325 has a knurled head and a threaded shank and is adjusted inwardly to dress the stone 327. By rotating the dresser, the head portion of the dresser is moved toward or away from the grinding stone.

ALTERNATE SWING ARM ASSEMBLY Referring finally to FIGS. 17 and 18, there is shown a swing arm arrangement and assembly 350. This arrangement includes a short leg member 352 having a shouldered slot 354 and is adjustably mounted and clamped in sloped recess 310 by means of socket head cap screw 314 mounted also in the threaded hole 312 which is formed in support block 220. Also carried in a T-shaped hole 358 formed in the block 228 in a T-block or bar 360 Whose reduced inner end is engaged by a set screw 362 adjustably carried in the threaded portion of hole 358. Pivotally carried on the reduced or right end of leg member 352 is swing arm 366 which carries on its other end the diamond dresser 325 which is mounted in a threaded hole 368 formed in this arm 366.

The pivot connection between leg member 352 and swing arm 366 includes a headed pin 370 which in the present embodiment is threaded throughout its axial length. In arm 366 there is provided a radial ball bearing 372 carried in a precise recess formed in the arm. Between leg member 352 and arm 366 and axially carried on pin 370 is a roller thrust bearing 374. The upper end of pin 370 is journaled in a precisely sized hole in the end of leg member 352. The two race members 376 and 377 of the bearing 374 (FIG. 18) have their facing outer edges charnfered to provide a retaining groove in which is mounted an O-ring 380. This O-ring is preferably of rubber and is of a selected size so that in a mounted condition it is stretched and frictionally engages each chamfered surface 382 and 383 (FIG. 18) to act as a drag or brake against the rotation of the races 376 and 377. In addition to acting as a brake, the O-ring is also a dirt or dust shield to prevent dirt and particularly grinding dust particles from entering the thrust bearing 374.

A Belleville washer or spring 386 is engaged by the head of adjusted screw 388 so as to provide the desired amount of thrust load on the bearing 374. A set screw 390 is carried in the threaded portion of the headed pin 370 and after the screw 388 has been tightened to cause a desired tension of spring 386 the set screw 390 is advanced in the threaded hole sos as to lock screw 388 in its adjusted position.

USE AND ADJUSTMENT OF THE SWING ARM ASSEMBLY OF FIGS. 17 AND 18 With the screw 388 tightened to cause spring 386 to exert the desired thrust on hearing 374, the O-ring 380 acts as a brake which tends to retain the swing arm 366 in its adjusted radial relationship to leg 352 until the arm 366 is rotated around pin 370 to a new position. The angle of dressing of the stone is precisely and selectively accomplished by adjusting the relationship of leg 352 to the base of recess 310. Screw 314 is loosened and set screw 362 is advanced or reversed in the threaded hole in support block 220. The movement of the set screw permits T-block 360 to be moved further into and from the base of recess 310. After screw 362 has been adjusted as required, the cap screw 314 is tightened to clamp leg member 352 in recess 310 at the selected angle to which the stone is to be dressed. Of course, when the dressing has been accomplished the arm 366 is rotated to an out-of-the-way position whereat the O-ring 380 maintains the arm in this storage position.

USE AND OPERATION OF CENTER-HOLE GRINDER In use, the center-hole grinder is positioned so that the pedestal 24 is substantially in an upright condition. A pair of steady-rest side blocks such as the side blocks 138 and 139 of FIG. are mounted on clamp bar 136. The workpiece whose center-hole is to be ground is vertically positioned with its bottom end resting on the bottom drive center 88 of worktable 70 and the upper end resting in the forty-five degree V-type steady-rest. The slide blocks and support pins 150 and 151 are adjusted until the axis of the workpiece is disposed at a four degree angle off the vertical and tilted rearwardly toward the pedestal. The V-type steady-rest is moved up and down on the T-bar 66, to accommodate the workpiece being ground, but is positioned at the highest possible position, towards the center being ground.

The V-type steady-rest is constructed so as to have a trombone movement. This movement occurs when the slide stop 176 is moved to the right or from in way of the end of plunger member 166 permitting the steadyrest to oscillate horizontally on the shafts 126 and 128. With the plunger 172 in contact with the face of the block 120, the grinding point at a lower portion of its stroke is positioned to contact the inner or back side of the centerhole being ground. This adjustment is provided by the raising or lowering of table 70 by rotating the screw 40 to bring the end of the workpiece to the level of the grinding stone. The head 26 is then moved backwardly and forwardly upon the pedestal 24 by manipulating or rotating knob 236. After the grinding stone has been brought into contact with the inner or back portion of the center-hole of the workpiece, the lever 240 is manipulated to raise and lower the rotating grinding point or stone so that the grinding stone is brought into engagement with the center-hole workpiece. As the center-hole of the workpiece is engaged and ground, the side pressure causes the workpiece to be deflected inwardly, causing the steady-rest to move inwardly against the compression of spring 170. This trombone movement produces a grinding action which causes a convex radius to be generated on the thirty degree side or slope of the centerhole.

The depth of the grind may be mechanically controlled by means of a stop, not shown. This stop allows the grinding point to bottom and clear itself at the downwardmost depth of the grinding stroke. A speed control, as shown by knob 350 on FIG. 1, is contemplated to provide a speed differential of the rotation of the grinding stone from about one hundred r.p.m. to a top speed of about forty thousand r.p.m. To grind a perfectly true center-hole with no convex radius, the trombone action is cancelled by locking the steady-rest position. At the same time, the stop 176 is slid into plunger engaging position with the end of adjusting screw 166. The locking screws 132 and 133 are then advanced inwardly to retain shafts 126 and 128 in the fixed position.

If the diameter of the part being round is too much out-of-round to permit a satisfactory center-hole to be ground, and OD. grinding of the out-of-round journal is required. With the part resting in the V-type steadyrest, the trombone movement will determine whether the grinding of the center-hole produces a center-hole whic his straight-sided or has a convex-sided center-hole. as seen in FIG. 16, wherein the workpiece 340 has an internally ground center-hole 342 with a slightly convex surface 344 which is disposed to engage a center 346 at a single line contact.

It is to be noted, of course, that the support bar 136 permits the moving in and out and adjusting thereon of the various support blocks. The adjusting screws or support surfaces of these support blocks are disposed to provide a steady-rest with forty-five degree support points. The steady-rest, where magnets are used, additionally attracts the part towards the magnet and into the V-support so that the part may be freely rotated against and in the steady-rest. The four degree tilt causes the workpiece to bear against the support so as to be securely retained in this upper V-type support. The grinding of the center-hole causes an additional thrust against the back of the hole and insures that the part is thrust toward and into the V.

When it is desired to dress the stone of the grinding wheel, the lever 240 is manipulated to bring the grinding stone to a desired position whereupon the set screw 306 of FIG. 12 is manipulated inwardly to cause the balls 301 and 302 to thrust forwardly against the thrust bar 290. As the ball 302 enters the notch 296, the beveled ends of the bar are thrust against the shafts 266 and 267 to lock block 28 against up-and-down movement. The arm 320 of the dressing head of FIGS. 13, 14 and 15 or arm 366 of FIG. 17 is then rotated until the diamond dresser is brought adjacent the stone whereupon the head of the dresser is rotated to bring the dressing head 325 inwardly into engagement with the stone 327. The leg member 318 or 352 is slid up and down in the notch 310 until the arm 320 or 366 is substantially at right angles to the axis of the stone when the stone is at the desired dressing position. The diamond dresser, of course, is moved up and out of the way while and during the time that the grinding stone is grinding the center-hole of the workpiece. It is also, of course, certainly apparent that after one end of the workpiece has its center-hole ground true, that the workpiece is removed from the center-hole grinder and reversed end-for-end. The other center-hole of the workpiece is then ground true. The up-and-down movement of table 70 is readily accomplished by means of rotating the screw 40 clockwise or counterclockwise. The rotational drive of the workpiece is accomplished by causing the motor in the worktable to be rotated. Appropriate clamping means such as a lathe dog is used to insure that the workpiece is driven at the desired speed provided by the worktable motor.

It is recognized that when it is required to true up the outer journal surface of a workpiece, the V-type steadyrest may be adjusted to remove the trombone effect. This, as above-noted, requires slide stop 176 to be moved into engagement with the inner end of plunger, member 166 and/or clamp screws 132 and 133 to be tightened against shafts 126 and 128. Head member 26 is moved outwardly until the grinding stone, in its reciprocating cycle, is positioned to grind the outermost portion of the journal surface as the stone is vertically reciprocated.

In grinding the center-hole, the amount of convex curvature formed in the center-hole is controlled by the up-and-down traversing speed provided by the manipulation of lever 240. The periods of dwell at each end of the cycle are also a contributing factor to the are formed in the sloped side of the center-hole which is ground.

Terms such as left, right, up down, bottom, top, front, back, in, out and the like are applicable to the embodiments shown and described in conjunction with the drawings. These terms are merely for the purposes of description and do not necessarily apply to the position in which the centerhole grinder and its V-type steady-rests may be constructed or used.

The conception of the center-hole grinder and its many applications is not limited to the specific embodiments shown but departures therefrom may be made, within the scope of the accompaning claims and protection is sought to the broadest extent the prior art allows.

I claim:

1. A center-hole grinder for accurately grinding the center-hole portions of workpieces wherein each workpiece, as it is being ground, is supported in a generally vertical attitude and at a selected speed is rotated as the center-hole is being ground, the center-hole grinder including:

(a) a base;

(b) a pedestal member carried by the base;

(c) a guideway member carried at least in part by the pedestal member;

(d) a drive table carried by the guideway member and having means for rotating a workpiece carried thereon at a selected speed;

(e) a steady-rest carried by the quideway member, the steady-rest having adjustable means for rotatably supporting a workpiece near its upper end and to support said workpiece so as to be inclined toward the pedestal and at a slight angle to a vertical condition;

(f) a head member carried by the pedestal and movable thereon and transversely to the axis of the workpiece;

(g) a motor housing bracket reciprocably carried in the head member and providing means for retaining a grinding motor with a grind stone in the bracket, and

(h) means for cycling the motor housing bracket up and down to bring the motor driven grind stone into selective engagement with the center-hole being ground.

2. A center-hole grinder as in claim 1 in which the guideway member is a T-bar carried by both the base and pedestal and in which the drive table is slidable on the T-bar and is moved up and down therein by means of an elevating means.

3. A center-hole grinder as in claim 2 in which the elevating means is a lead screw carried by the base and pedestal, said screw being rotated by a motor means and with said lead screw threadedly engaging a mating threaded nut in the drive table to move the table up and down the T-bar.

4. A center-hole grinder as in claim 3 in which the lead screw is positioned so as to be parellel to the T-bar and in which both lead screw and T-bar are inclined at about four degrees from the vertical and toward the pedestal.

5. A center-hole grinder as in claim 3 in which the drive table has a rotatable member which is driven by power means at a selected speed, said rotatable member having means for engaging and driving the workpiece at the same speed as the rotatable member of the drive table.

6. A center-hole grinder as in claim 5 in which the means for engaging and driving the workpiece is a pin mounted in the rotatable member, said pin disposed to engage and drive a lathe dog and the like.

7. A center-hole grinder as in claim 5 in which the rotatable member of the drive table has a socket disposed for removably retaining a center, said rotatable member being driven by a gear motor carried by the worktable.

8. A center-hole grinder as in claim 3 in which the motor driving the lead screw is a reversible gear motor and the drive from the motor to the screw includes a pulley on both screw and motor and the power transmitting means from the motor pulley to the screw pulley is provided by a timing belt, roller chain and the like.

9. A center-hole grinder as in claim 3 in which the steady-rest provides a V-type support for the workpiece, said steady-rest having a support body disposed to engage and slide upon the T-bar, the support body having a pair of parallel passageways formed therein and with said passageways adapted to reciprocably retain a pair of shafts which are attached at one end to a support bar, the support bar having means for adjustably carrying a pair of slide blocks, each slide block having means for slidably engaging and supporting a workpiece as it is turned, and means for clamping the shafts in a determined position in the passageways.

10. A center-hole grinder as in claim 9 in which there is a plunger body which is mounted in and carried by the support bar, said plunger body being adjustable toward and away from the support body, said plunger body further having a biased means disposed for engaging the support body and urging the support bar away from the support body to permit a trombone movement of the support bar and shafts against the bias provided in the plunger body.

11. A center-hole grinder as in claim 10 in which the plunger body has a plunger pin extending a determined distance therefrom, the plunger pin engaging a compression spring which provides the bias means for urging the support bar away from the support body.

12. A center-hole grinder as in claim 11 in which there is provided a slide stop on the support body, said slide stop disposed so as to be moved into and out of engagement with the plunger body so as to negate the bias action of the plunger pin.

13. A center-hole grinder as in claim 9 in which the parallel passageways in the support body are provided with ball bushings sized to precisely and reciprocably retain the parallel shafts at right angles to the axis of the supported workpiece.

14. A center-hole grinder as in claim 9 in which the support bar has a dovetail formed therein and in which there are provided slide nuts sized to slide in said dovetail and in which the slide blocks each have formed therein a contoured guide means disposed to slide on a mating guide means formed on the support bar and in which a clamp screw is disposed to pass through a passageway formed in the slide block and engage a threaded portion in the slide nut so that with the clamp screw in a loosened condition the slide block may be moved along the support bar in a determined path and with the clamp screw tightened to draw the slide nut into locking engagement with the dovetail, the slide block is drawn into retaining engagement with the support bar.

15. A center-hole grinder as in claim 14 in which the support bar is of a straight configuration with its upper edges beveled to provide a guide edge and guide means which mates with and enters a contoured groove and guide in the slide block.

16. A center-hole grinder as in claim 14 in which there is carried in each slide block a threaded support pin having its inner end conditioned to slidably engage and support a workpiece, the support pins disposed at an angle of about twenty-two and one-half degrees to a common plane with the resulting disposition of the inner ends of the pins providing a V-type support of about forty-five degrees included angle.

17. A center-hole grinder as in claim 16 in which the support pins are antimagnetic and in which the slide blocks are provided with means for providing a magnetic attraction to draw the workpiece toward the slide blocks.

18. A center-hole grinder as in claim 17 in which the magnetic attraction includes making the slide blocks of an anti-magnetic material and in which cylindrical magnets are carried in said slide blocks with an insulating sleeve provided in each magnetic assembly, the sleeve providinga passageway and means for carrying and rtatably retaining a support pin.

19. A center-hole grinder as in claim in which the slide blocks are each provided with a support surface disposed at about sixty-seven and one-half degrees to the contoured guide means for the guide edge of the support bar, said support surface providing a minimal sliding friction with the journal of a workpiece, the slide blocks disposed to be arranged as a facing pair so that when clamped to the support bar the facing support surfaces provide a V-guide support of about forty-five degrees included angle.

20. A center-hole grinder as in claim 19 in which a clamp member having a curved end is disposed to adjustably engage an outer diameter of a journal of a workpiece, said clamp member movably retained on a support block so as to urge the workpiece into sliding engagement with the V-guide support surfaces.

21. A center-hole grinder as in claim 15 in which each slide block is :provided with a roller which is mounted and positioned so as to be moved into supporting engagement with the inner diameter of a tubular end of a workpiece.

22. A center-hole grinder as in claim 3 in which the head member portion has a slide member which is slidably mounted in a dovetail guideway on the support pedestal and in which there is provided a rack-and-pinion means for selectively moving the head member in the dovetail giudeway and in which there are means for clamping the head member in said dovetail.

23. A center-hole grinder as in claim 3 in which the means for cycling the motor housing bracket is a rackand-piston assembly, the pinion being carried on a shaft carried in the head member and the rack carried by the motor housing bracket, and in which there are means for clamping the motor housing bracket at a determined position in its up-and-down limit of motion.

24. A center-hole grinder as in claim 23 in which the motor housing bracket is carried on shafts mounted in the head member and in which antifriction means are carried in said housing bracket for moving said bracket on the shafts.

25. A center-hole grinder as in claim 24 in which the antifriction means are ball bushings carried in shaft bores in the motor bracket.

26. A center-hole grinder as in claim 24 in which a spring means is provided so as to bias the motor bracket to the upper limit of its movement and in which the means for clamping the housing bracket on the shafts includes a thrust bar sized to be slidably retained in a passageway formed in the head member, said thrust bar having its ends contoured and spaced so as to lie between and contiguously to the facing sides of the pair of shafts, said thrust bar further having a notch formed in its side and intermediate its ends and with the bar being tapered toward its ends and with the taper disposed on the side opposite the notch and in which there is provided means for entering the notch so as to bend the bar to cause the ends to engage the pair of shafts to lock the motor bracket from a cycling motion.

27. A center-hole grinder as in claim 26 in which the means for entering the notch is a ball which is carried in and is movable in a formed passageway in the head member and is pressed into said notch by means of the forward motion of a screw carried in a threaded hole in the head member, said screw having a tapered end which is disposed to engage the ball and move the ball into said notch.

28. A center-hole grinder as in claim 3 in which there is provided an adjustable diamond dressing means including a swing arm arrangement which is adapted to permit a diamond dresser to be moved to a position adjacent a grinding stone carried in the grinding motor and in which there is an adjusting means for moving the diamond dresser into dressing engagement with the stone.

29. A center-hole grinder as in claim 28 in which the diamond dresser has a large dressing face defining a dressing surface which, as it is brought into engagement with the stone being dressed, simultaneously generates a straight surface on the side of the rotating stone.

30. A center-hole grinder as in claim 29 in which the dressing face of the diamond dresser is a flat circular face having a multiplicity of exposed diamond points disposed to lie in a plane in said flat face, and in which the adjusting means is a threaded shank which supports and carries the diamond dresser head, the threaded shank being rotatably carried in a threaded hole in the swing arm arrangement.

31. A center-hole grinder as in claim 30 in which the swing arm arrangement includes a swing arm pivotally mounted and carried on a leg member adjustably mounted on the head member.

32. A center-hole grinder as in claim 29 in which the swing arm arrangement includes a pivoted connection between a supporting leg member and a swing arm, the connection including a pin member joining the leg member and swing arm; a thrust bearing carried by the pin member and rotatably separating the leg member and swing arm; means for providing a determined thrust of the swing member towards the leg member, and resilient means engaging race members of the thrust bearing so as to provide a drag or brake on the rotational movement of the race members.

33. A center-hole grinder as in claim 32 in which the thrust bearing has two thrust plate race members of circular configuration, the members having opposed facing edges chamfered to provide a groove in the assembled bearing and in which the resilient means is an O-ring which is snugly mounted under tension in said groove.

34. A center-hole grinder as in claim 33 in which the means for providing a determined thrust is a spring washer.

35. A center-hole grinder as in claim 32 in which the References Cited leg member is longitudinally adjustably carried in a UNITED STATES PATENTS sloped recess in the head member and in which there is provided a T-block adapted to be adjustably moved into 3187470 6/1965 Ameson 51 89 and from the sloped recess and locked in a selected position so as to engage a portion of the leg member and 5 WILLIAM ARMSTRONG Pnmary Exammer means for clamping the leg member at a determined Us Cl XR angle in the recess with a portion of the leg member 2381 supported by the T-block. 

